We regularly test water quality at popular swimming and surfing beaches to determine any health risks that may be caused by wastewater discharge from the Tahuna outfall. Enterococci is the measure used.
You can find results for city beaches from Lawa website - beach quality (link to external website, new window)
What are enterococci
Enterococci are bacteria found in the gut of humans, birds and other warm-blooded animals. They indicate the presence of faecal material in seawater. They are used as ‘indicator organisms’: the more of these there are, the more likely it is that pathogens, such as viruses, are also present.
MfE guidelines for beach water tests
The Ministry for the Environment has set water quality guidelines for recreational water use. They use a ‘traffic light’ approach.
Continue routine monitoring
Acceptable – alert
Increase monitoring and investigate source
Unacceptable – action
Re-sample immediately, issue a public warning if required, increase monitoring and investigate source
Where and when we monitor
Testing is carried out monthly from April to October and weekly from November to March at the following places:
- St Clair Beach
- Middle Beach
- St Kilda Beach
- Lawyers Head Beach
- Tomahawk Beach west
- Sandfly Bay
We flush the outfall for about ten minutes each day. You might see a plume for about half an hour after the flushing and during rain because the flows are much higher than normal.
Eight diffuser units at the end of the outfall spread the treated wastewater over a large area so it can mix thoroughly with seawater.
Foam on beaches
Foam may look unsightly and even smell bad, but it is not raw sewage. Foam contains algae, tiny particles of decaying seaweed, small crustaceans, planktonic animals, sand and sediment – all bound together in a mucus film.
Foam tends to be more common in the summer when algal growth is at its peak. The runoff of nutrients, such as fertiliser, from land may make the problem worse by encouraging algae to flourish near the shoreline. When the density of algae is high enough, a brown or yellow ‘bloom’ will appear in the water. The algae eventually die off and are whipped into foam by the surf. The foam then traps other debris and forms a brown scum that gets left on the beach when the tide goes out.
We have tested foam for faecal contamination and the tests usually show very low concentrations of bacteria.
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